Cataloging Diversity Across The Americas

“What trees! … all utterly new to us; Bonpland keeps telling me he’ll go out of his mind if the wonders don’t cease soon.”

Alexander von Humboldt words of excitement when first landing in present day Venezuela in 1799 demonstrate the exuberance of plant diversity botanists working in the New World face. Beans, cashews, corn, potatoes, tomatoes, peppers, pineapple, quinine, tobacco, rubber, sunflower, and vanilla are all among the magnitude of plants native to the Americas.

Naturalists and plant scientists have been collecting plants across this region for five hundred years. They’ve dried and pressed them, studied and named them, and stored away in the herbaria of the world more than 22 million specimens. Yet after centuries of collecting, an average of 744 species are described as new to science every year.

Until recently, this overwhelming wealth of diversity and information has been documented only in disparate lists and catalogs. With the publication of “An integrated assessment of the vascular plant species of the Americas” in the December 2017 issue of Science, an international team of 24 researchers led by Missouri Botanical Garden botanist Dr. Carmen Ulloa has for the first time provided a comprehensive overview of all known plants of the Western Hemisphere.

Diversity in Digits

124,993 species, or one-third of the world’s known vascular plants (ferns, conifers, and flowering plants) are found in the Americas.

There are 51,241 species of vascular plants in North America and 82,052 in South America.

Only 8,300 of the species are shared between North and South America.

South America has 6% more species of vascular plants than Africa but is only half its size.

The orchids (Orchidaceae) are the largest family with 12,983 species; second is the sunflower family (Asteraceae) with 12,043 species, and third the legumes (Fabaceae) with 7,473 species.

52 plant families are restricted (or nearly restricted) to the Americas. The pineapple family (Bromeliaceae) is the largest of these families with 3,403 species; second is the cactus family (Cactaceae) with 1,847 species.

Brazil is the country with the most species of vascular plants in the Americas, 33,161. Colombia is second with 23,104, and Mexico is third with 22,969.

The highest concentration of plant diversity is in Ecuador (17,548 species in an area of 256,370 km2).

The authors predict there will be a total of 150,000 species of vascular plants documented by 2050.

Tillandsia usneoides, “Spanish moss,” neither Spanish nor a moss, a widespread species native to the New World, in the pineapple family Bromeliaceae, a family nearly restricted to the Americas. Photo S. Keil.

Faced by a growing need to rapidly document the abundance of plants threatened by human activities, the Garden initiated a series of country-based plant checklists in the 1990s. Other institutions followed with additional lists, resulting in complete plant inventories for Mexico, the West Indies, and all of South America, as well as partial checklists for Central America and North American regions north of Mexico. Ulloa and her colleagues have merged all of the information from these regional checklists into one massive compendium. Hosted on the Garden’s Tropicos® plant database, this continuously updated, searchable database is publicly accessible and now includes all 124,993 species of plants currently known from the Western Hemisphere.

Beyond the benefit provided to other plant scientists, this new database represents “a monumental achievement that will be of enormous interest to conservation biologists, ecologists, evolutionary biologists, biogeographers, land managers, and governmental officials around the world,” according to noted botanist Dr. Thomas Givnish.

The hope is that conservationists will use the database to manage a country’s or region’s plant assets, says Dr. Ulloa. “Now we know what we can conserve.”

Other current or former members of the Garden research staff involved in this study include co-authors Dr. Gerrit Davidse, Heather Stimmel, Dr. James Zarucchi, Dr. Peter Jørgensen, Dr. Robert Magill, and Garden President Emeritus Dr. Peter Raven. Dr. Tom Croat and Dr. Charlotte Taylor are acknowledged for having described more than 400 plant species in the database.